Manet network management

ABSTRACT

Mobile ad hoc Network (MANET) includes a first node of a plurality of nodes which self-assigns a role as a part of a network-spanning backbone upon a determination by the first node that one or more criteria have been satisfied. The first node uses the network-spanning backbone to facilitate a first-tier control plane communication service within the MANET. The first node also communicates within the MANET using a second-tier control plane communication service separate from the first-tier control plane communication service. The second-tier control plane communication service is used by the first node when communicating exclusively with neighbor nodes that are a 1-hop distance from the first node.

BACKGROUND Statement of the Technical Field

The inventive arrangements relate to communication networks, and moreparticularly to methods and systems for managing mobile ad-hoc networks.

DESCRIPTION OF THE RELATED ART

A mobile ad-hoc network (MANET) is a wireless self-configuring networkin which data is communicated from one or more source nodes to at leastone destination node in a series of wireless hops which can traverse oneor more nodes. New nodes can be configured to automatically join with anexisting network when in wireless range of the one or more nodes thatform the MANET. The nodes forming a MANET can be stationary or mobile.Further, each node in the network is commonly configured so that it canfunction in the role of a terminal node and/or a router for other nodesin the network. An important aspect of a MANET is that the nodes areself-organized and without a fixed topology. As a result of theforegoing, the topology of a MANET is often highly variable and canchange in ways that are difficult to predict.

All MANETs are resource constrained, with only so many over the air(OTA) resources available. This results in certain constraints beingplaced upon the control and operation of such networks. In somescenarios, it is desirable for a MANET to have a low probability ofdetection (LPD). This goal can add further constraints to the way inwhich the network is implemented. For example, one way in which a MANETcan reduce the probability of detection is by reducing over the air(OTA) traffic as much as possible. Still, there are certain aspects of aMANET that require OTA traffic. For example, in order to forward trafficefficiently to network destinations, nodes must learn about the networkaround them, in a process known as Network Discovery. Such informationcan involve the total number of nodes comprising the network, theidentity of those nodes, available routes to those nodes, and distanceto the nodes. As the number of nodes in a MANET increases, there is atendency for OTA traffic to also increase.

SUMMARY

Embodiments concern a Mobile ad hoc Network (MANET) and methods formanaging same. The method can involve self-assigning by a first node ofa plurality of nodes comprising the MANET a role as a part of anetwork-spanning backbone upon a determination by the first node thatone or more criteria have been satisfied. In so doing, the first nodecan assume the role of a cluster-head node which comprises a part of afirst-tier control plane communication service. Thereafter, the firstnode uses the network-spanning backbone to help facilitate thefirst-tier control plane communication service within the MANET. Themethod further involves communicating by the first node within the MANETusing a second-tier control plane communication service separate fromthe first-tier control plane communication service when communicatingexclusively with neighbor nodes that are a 1-hop distance from the firstnode.

According to one aspect, the method can further involve choosing by thefirst node one or more bridge nodes of said first tier control planecommunication service which facilitate communication by the first-nodewith neighbor nodes that are a 2-hop distance from the first node.Thereafter, the first node uses the network-spanning backbone tofacilitate communication with all nodes of the network. The method canfurther involve choosing by the first node a cluster ID corresponding toa set of time slots in a Time Division Multiple Access (TDMA) waveform.

The first node uses the network-spanning backbone to facilitatede-confliction of the cluster ID. The first node can also use thenetwork-spanning backbone to communicate information concerning all ofits 1-hop neighbors to the plurality of nodes comprising the MANET. Theabove-described process involving the first node can similarly occurconcurrently in different places in the network. Accordingly, othernodes can also become cluster-head nodes. Together all of theseself-assigned cluster-head nodes form a part of the network-spanningbackbone to facilitate the various communication services.

Embodiments also include a communication node for carrying out themethods described herein for communicating in a Mobile ad hoc Network(MANET). The communication node includes a communication transceiverconfigured to facilitate wireless communications between thecommunication node and other nodes of the MANET. The communication nodealso includes a computer processor device. The computer processor deviceis configured to self-assign to the communication node a role as a partof a network-spanning backbone of the MANET upon a determination by thecommunication node that one or more criteria have been satisfied. Thenetwork spanning backbone is comprised of a plurality of nodes of theMANET. According to a further aspect, the computer processor device isconfigured to cause the communication node to use the network-spanningbackbone to facilitate communication with all nodes of the network.

The computer processor device is also configured to cause thecommunication node to use the network-spanning backbone to facilitate afirst-tier control plane communication service within the MANET and tocommunicate within the MANET using a second-tier control planecommunication service. The second-tier control plane communicationservice is separate from the first-tier control plane communicationservice and is used by the communication node for communicatingexclusively with neighbor nodes that are a 1-hop distance from thecommunication node.

Upon assuming a role for the communication node as part of thenetwork-spanning backbone, the computer processor device can choose oneor more bridge nodes of the first-tier control plane communicationservice. The one or more bridge nodes can be used to facilitatecommunication by the communication node with one or more neighbor nodesthat are a 2-hop distance from the communication node.

The self-assigned role chosen by the communication node can be as acluster-head in the first-tier control plane communication service. Insuch a scenario, the computer processor device can be further configuredto choose a cluster ID corresponding to a set of time slots in a TimeDivision Multiple Access (TDMA) waveform. In this regard, the computerprocessor device can be further configured to cause the communicationnode to use the network-spanning backbone to facilitate de-conflictionof the cluster ID.

The computer processor device can cause the communication node to usethe network-spanning backbone to communicate information concerning allof its 1-hop neighbors to the plurality of nodes comprising the MANET.According to a further aspect, the communication node can be configureduse an avalanche communication method to facilitate the first tiercontrol plane communication service in which identification thecommunication node as the source of transmitted messages is impliedbased on the time slot in which the message is communicated.

The computer processor device is configured to claim for thecommunication node a tier 2 beacon time slot of the TDMA waveform. Thecomputer processor device can also be configured to use the tier 2beacon time slot to confirm that the tier 2 beacon time slot is conflictfree within a 2-hop distance of the communication node. Thereafter, thecomputer processor device can cause the communication node to use thetier 2 beacon time slot to discover its neighbor nodes which are withina 2-hop distance of the communication node. The computer processordevice can be further configured to use the tier 2 beacon time slot todetermine a network role of each of the neighbor nodes within a 2-hopdistance of the communication node. The computer processor device canthen use information it has determined concerning the network role ofeach of the neighbor nodes within the 2-hop distance as a basis fordetermining whether the one or more criteria have been satisfied.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described with reference to the following drawingfigures, in which like numerals represent like items throughout thefigures, and in which:

FIG. 1 is a drawing that is useful for understanding a multi-hop MANETcomprising a plurality of nodes.

FIG. 2 is a drawing that is useful for understanding certain concepts ofa time division multiple access channel sharing arrangement.

FIG. 3 is a drawing that is useful for understanding a time-expandedview of a time division multiple access channel sharing arrangement.

FIG. 4 is a drawing that is useful for understanding a Tier 2 controlplane communication service in a MANET.

FIG. 5 is a drawing that is useful for understanding a Tier 1 controlplane communication service and network backbone provided in the MANETof FIG. 4 .

FIGS. 6A-6C are a set of drawings comprising a flowchart that is usefulfor understanding a rule set under which nodes in a MANET may adapttheir operation based on their discovered neighbors.

FIG. 7 is a drawing that is useful for understanding how data is relayedin a MANET given the TDMA nature of the underlying channel.

FIG. 8 is a block diagram which is useful for understanding acommunication node of a MANET.

FIG. 9 is a block diagram which is useful for understanding a processingunit of a communication node that can perform certain operations asdescribed herein for purposes of implementing a MANET network.

DETAILED DESCRIPTION

It will be readily understood that the components of the embodiments asgenerally described herein and illustrated in the appended figures couldbe arranged and designed in a wide variety of different configurations.Thus, the following more detailed description of various embodiments, asrepresented in the figures, is not intended to limit the scope of thepresent disclosure but is merely representative of various embodiments.While the various aspects of the embodiments are presented in drawings,the drawings are not necessarily drawn to scale unless specificallyindicated.

Embodiments disclosed herein may provide certain advantages in a MANETcommunication network. In particular, certain embodiments can improveperformance of such networks by utilizing a two-tiered mechanism fornetwork discovery and control plane communication. These two controlplanes, which are referred to herein as Tier 1 and Tier 2communications, facilitate and support the regular communication ofroutine voice and data traffic among the nodes of the network.

According to one aspect, all nodes in the network can hear transmissionson a Tier 1 communication backbone of the network. The Tier 1communication backbone applies certain clustering rules and utilizesavalanche communication methods. These techniques are described below infurther detail. However, it should be understood that an advantage ofthe Tier 1 communication backbone is that it provides a way to allow allnodes in the network efficiently discover the existence, androute-ability of all other nodes, while maintaining a low probability ofdetection. The Tier 2 communication service is a 1-hop local beaconservice that includes all nodes comprising the network. The Tier 1 andTier 2 control planes in combination facilitate a low overhead routingsolution that significantly reduces over-the-air traffic.

An example of a mobile ad-hoc network (MANET) 100 is shown in FIG. 1 .The MANET is a wireless self-organizing network in which data iscommunicated between a plurality of nodes 102 in a series of one or morewireless hops from a particular node 102 that is the source of acommunication to a different node 102 that is an intended recipient of aparticular communication. The nodes 102 which comprise the network 100can be stationary or mobile and it is understood that new nodes 102 canjoin the network automatically when in wireless range of any of theexisting nodes comprising the network. In a network access systemdescribed herein, each node 102 comprising the network 100 can functionin the role of a terminal node and/or a router for other nodes in thenetwork. Further, each node may be assigned certain identifyinginformation. For example, such identifying information can be amulti-bit digital identification value. This value is hereinaftersometimes referred herein as a node ID. As explained herein in furtherdetail, there is no single node that controls the network operation orprioritization of resources. Further, although a particular example of anetwork topology is shown in FIG. 1 , it should be understood that aMANET 100 as described herein is self-organized and therefore can haveany topology.

According to one aspect, a MANET described herein can operate inaccordance with a time division multiple access (TDMA) arrangement. Withreference to FIG. 2 , it will be understood that a particular RF channelin a TDMA based system can be divided into a plurality of time slots 104which are organized within a series of successive epochs 106. Each epochassociated with the TDMA waveform is comprised of a predefined number oftime slots 104. The epochs 106 can in some scenarios be numbered so thatdifferent epochs can be individually identified (e.g., epoch 1, epoch 2,. . . epoch n, epoch n+1 . . . ). In a TDMA based system the pluralityof nodes 102 can share and use the same RF channel. This is accomplishedby assigning nodes 102 permission to use various different time slots ofan RF channel for certain specified purposes.

Avalanche communications as that term is used herein involves a datarelay process in a MANET network in which two or more nodes transmit thesame data concurrently during the same time slot. This concept may beunderstood with reference to FIG. 1 . For example, assume that node Aseeks to communicate a message P to node E. During a first epoch T1,node A can transmit message P to nodes B and Y. During a second epochT2, the message P will be retransmitted concurrently during the sametime slot by nodes B and Y in a first relay operation. Assume that forsome reason, the relay transmission from node Y is not received by anyother node, but the relay transmission from node B is received by nodesC and D. Thereafter, in a third epoch T3, nodes C and D willconcurrently transmit during the same time slot to relay message P tothe nodes E and F. At the receiving end of such relay communication,nodes E and F will each treat the two nearly simultaneous messagestransmitted by C and D as multipath communication of the same message.This improves the chances of reception by nodes E and F, but also hasthe beneficial effect of improving bandwidth utilization since bothmessages are broadcast at the same time. This technique of concurrenttransmission of the same data by different nodes is referred to as anavalanche transmission method.

FIG. 3 shows a time-expanded view of a succession or series of threeepochs 201, 202, 203 comprising an example of a TDMA waveform which isuseful for understanding certain aspects of a solution presented herein.Within each epoch, certain time slots can be designated for certainpredetermined purposes. For example, in some scenarios a Sync time slot204 can contain time synchronization data to facilitate timing alignmentof the various nodes 102 comprising the network. Similarly, each epochcan contain a plurality of Tier 1 and Tier 2 beacon time slots. Theseslots are shown in FIG. 3 as Tier1 Bcn time slots 206 and Tier2 Bcn timeslots 208. These Tier 1 and Tier 2 beacon slots are used to facilitatecertain control plane communications which are discussed below infurther detail.

Certain time slots can also be reserved for data traffic communicatedamong the various nodes. For example, in FIG. 3 , each epoch includestime slots 210, 212, 214 which in this example are reserved for digitalvoice communications among certain talk groups (e.g., TG1, TG2 and TG3).In the scenario shown, these time slots 210, 212, 214 are respectivelylabeled Vce TG1, Vce TG2, and Vce TG3. Other time slots 216 can be usedfor communicating other types of routine data traffic among the nodescomprising network. Time slots used for data traffic can beadvantageously assigned dynamically to various nodes on an as-neededbasis. It should be understood that the specific arrangement of timeslots is not critical and alternative time slot assignments are possibleto facilitate various network control operations.

Further, it should be understood that in some scenarios time slot usagecan be multiplexed. Accordingly, there are some scenarios in whichcontrol plane and traffic communications can be allocated to data slotswhich may or may not map to a single specific TDMA time slot and may ormay not appear in every epoch. In this regard, FIG. 3 should beunderstood to merely represent one possible example of a TDMA waveformslot assignment and is not intended to be limiting. Likewise, it shouldbe understood that not all networks incorporating the solution disclosedherein will necessarily include the same number or position of slotassignments for control and data transmission.

In a network solution disclosed herein, two control plane communicationservices are facilitated. A first communication service is referred toas a Tier 1 service, and a second communication service is referred toas a Tier 2 service. The diagram shown in FIG. 4 is useful forunderstanding a Tier 2 communication service and the diagram shown inFIG. 5 is useful for understanding a Tier 1 communication service.

According to one aspect, a Tier 2 communication service becomesavailable first within a network and comprises all nodes in the network.To facilitate the Tier 2 communication service, each node 302 claims foritself a TDMA Tier 2 beacon slot and ensures that such slot isconflict-free within its 2-hop neighborhood. For purposes of thisdisclosure, the phrase “2-hop neighborhood” may be understood to includeall nearby nodes which are within a maximum of two network hops from aparticular node.

The precise method by which a Tier 2 beacon slot is selected and thenclaimed by a particular node is not critical and various mechanisms arepossible. However, in a network solution disclosed herein, this processof claiming a Tier 2 beacon slot will advantageously occur without theneed for centralized control and/or communication with a singular nodehaving overall network control responsibility. For example, in onescenario each node seeking to join a network can monitor networkcommunications to identify certain TDMA tier 2 beacon slots that are orare not in use. Alternatively, or in addition thereto, such monitoringcan involve certain control plane time slots associated with the TDMAwaveform that contain information relating to known Tier 2 beaconchannel usage. In other scenarios, various alternative types ofout-of-band signaling such as special dedicated RF control channels canalso be monitored for this purpose. Combinations of these variousmethodologies are also possible. In all such implementations, the goalwill be to allow joining nodes to gain access quickly and efficiently toa specific TDMA Tier 2 beacon slot that is conflict-free within its2-hop neighborhood.

Once a joining node has claimed a particular Tier 2 beacon time slot, itcan begin communicating with its 1-hop neighbor nodes in accordance withthe network Tier 2 communication service. In some scenarios, suchcommunications can initially involve receiving data transmitted fromnearby nodes. For example, all nodes will regularly publish datarevealing their knowledge of the 1-hop network environment within theTier 2 communication service. As such, the joining node will discoverparticular Tier 2 beacon time slots which are available for use. Thejoining node can also obtain from its 1-hop neighbors certaininformation about neighbor nodes within its 2-hop neighborhood. Inparticular, the joining node can receive from its 1-hop neighbor nodesinformation concerning their identity (node ID) and any network rolestatus that they may have acquired. Finally, the joining node will alsoreceive from 1-hop neighbor nodes information concerning the identity(node ID) and network role status that has been acquired by any 2-hopneighbor nodes.

As will be understood from FIG. 4 , a MANET 300 comprised of nodes 302can include a Tier 2, 1-hop, local beacon service. The Tier 2 beaconservice includes all nodes 302 which are part of the network. To helpillustrate this concept, the nodes 302 are shown in circles 304. Thenodes within each circle can be thought of as logical groupings of nodesthat can all communicate with each other within one network hop, usingthe Tier 2 beacon service.

The same network 300 that is shown in FIG. 4 is also shown in FIG. 5 .It can be observed in FIG. 5 that some of the network nodes 302 whichparticipate in the Tier 2 communication service will also participate ina Tier 1 communication service. In particular, once a node has acquiredinformation concerning the identity and the network role of nodes withinits 2-hop neighborhood, it will determine whether to assign itself aparticular network role as part of the Tier 1 communication service. Forexample, such a node may determine whether to assign itself a networkrole as a cluster head node 306. This determination can be based on theapplication of a set of predetermined rules which are known to eachnode. If the rules, and/or the conditions set by the rules aresatisfied, then the node will determine that it is a cluster head 306.As used herein, cluster head nodes are those nodes which are permittedto originate data transmissions on the Tier 1 communication service.

The rules set applied by the network nodes can be summarized as follows:

-   -   Rule 1A: If a node does not hear a cluster head in its        1-hop-neighborhood, it will declare itself a cluster head after        a timeout period. In some scenarios, this timeout period can        have a duration which is randomized (e.g., one beacon cycle plus        some random number of elapsed epochs between zero and a second        beacon cycle).    -   Rule 1B: If a node hears a cluster head in its 1-hop        neighborhood, it will declare itself a leaf node and will only        promote itself to cluster head if it is unable to verify a        symmetric link to the heard cluster head after a timeout period        (Rule 1A). This timeout period can also have a duration which is        randomized. For example, the duration can include 3 beacon        cycles plus some random number of epochs from zero to beacon        cycle. This timeout period allows the cluster head node three        opportunities to hear the potential leaf node.    -   Rule 2: If a cluster head hears another cluster head and the        link is symmetric, it will step down to a leaf node.    -   Rule 3: All nodes need (at least) one 2-hop-neighborhood-unique        TDMA Tier 2 routine beacon slot/mux.    -   Rule 4: A cluster head will select bridge nodes from the set of        nodes in its symmetric 1-hop neighborhood that in turn have        symmetric links to at least one additional node in the 2-hop        neighborhood of the cluster head.    -   Rule 5: bridge nodes will step down to a leaf node if all        cluster heads that previously selected it are no longer        selecting it.    -   Rule 6: A cluster head node will select bridge nodes using a        first-discovered path selection algorithm.

In the foregoing rule set, Rule 1A applies to a disassociated node(i.e., a node that is starting up and does not yet have a defined role),to leaf nodes and to bridge nodes. If the node does not have or acquirea symmetrical relationship with a cluster head within a predeterminedtime limit, the node will then declare itself to be a cluster head. Aflowchart is provided in FIGS. 6A-6C that is useful for understandingthe set of rules applied by each node. The process begins in FIG. 6A at602 and continues to 604 where a node listens to determine if it canreceive signals from any nearby cluster head (CH) node. At 606 adetermination is made as to whether the node can hear a cluster head inits 1-hop neighborhood. If so, (606: Yes) it will declare itself a leafnode at 618. However, if the node cannot hear a cluster head node in its1-hop neighborhood (606: No), the node will declare itself to be acluster head node at 608. Such a node will then proceed at 610 to selectbridge nodes from the set of nodes in its symmetric 1-hop neighborhood(nodes within 1-hop that it can successfully transmit to and receivefrom). A condition placed upon such nodes which are to be designated asbridge nodes is that they have symmetric links to at least oneadditional node in the 2-hop neighborhood of the cluster head node.

The process continues at 612 in which the node continues to operate as acluster head node. The cluster head node will periodically check at 614to determine whether it hears any other cluster head nodes within 1-hop.If so (614: Yes), and the link is determined to be symmetric (616: Yes),then the cluster head node will relinquish its role as a cluster headand will become a leaf node at 618.

A node will check at 620 to verify that it has a symmetric link to theother cluster head node within 1-hop. If the link is verified (620:Yes), the node will continue at 622 in its role as a leaf node. However,if no symmetric link to the detected cluster head node can beestablished (620: No), then the leaf node will revert at 604 to itsformer condition.

Once a node declares itself as a leaf node, the process will continue onto 624 in FIG. 6B where a determination can be made as to whether thenode has been assigned a role as a bridge node. If so (624: Yes), thenode will assume the role of a bridge node at 626 and the process willcontinue on to 628. At 628, the node will periodically check todetermine whether it can continue to hear a cluster head node within its1-hop neighborhood. If so, (628: Yes) and the link is symmetric (630:Yes) then node will continue in its role as a bridge node. If the bridgenode can no longer hear a cluster head node (628: No) and/or the link isfound not to be symmetric (630: No) then the node which had beenoperating as a bridge node will instead return to 608 and declare itselfto be a cluster head node.

A leaf node which has not been assigned a role as bridge node (624: No)and/or a bridge node that has been de-selected (632: Yes) will functionas a leaf node. As shown in FIG. 6C, such a node will periodically checkto determine whether it can hear a cluster-head node within 1-hop (636:Yes) and that the communication link with such cluster head is symmetric(638: Yes). If these conditions are met, the node will continue as aleaf node and the process returns to 624. However, if the leaf node canno longer hear a cluster head node or determines that the link is nolonger symmetric, then the process returns to 608 and the node declaresitself a cluster head.

A node which has designated itself a network role as a cluster head orTier 1 transmitter will choose a cluster ID corresponding to a set ofTDMA Tier 1 beacon slots 206. The precise method by which a cluster headnode selects its cluster ID and corresponding Tier 1 beacon slots (seeFIG. 3 ) is not critical and various mechanisms are possible. However,in a network solution disclosed herein, the process of selecting suchslots will advantageously occur without the need for centralized controland/or communication with a singular node having overall network controlresponsibility. For example, in one scenario a cluster head can monitorTier 1 network communications to identify certain Tier 1 beacon slotsthat are or are not in use. Alternatively, or in addition thereto, suchmonitoring can involve certain control plane time slots associated withthe TDMA waveform that contain information relating to known Tier 1beacon channel usage. In other scenarios, various alternative types ofout-of-band signaling such as special dedicated RF control channels canalso be monitored for this purpose. Combinations of these variousmethodologies are also possible. In all such implementations, the goalwill be to allow those nodes which self-select to become cluster headsto quickly and efficiently gain access to a specific set of TDMA Tier 1beacon slots that are conflict-free.

Referring again to FIG. 5 , a node 302 which has assigned to itself anetwork role as a cluster head 306 will subsequently assign to one ormore of its 1-hop neighbors a network role as a bridge node 308. Bridgenodes or bridges are nodes that are chosen by cluster heads based ontheir ability to communicate with nodes that are 2-hop neighbors of thecluster head node. If a cluster head node 306 determines that aparticular 1-hop neighbor node is needed to reach 2-hop neighbors, itcan choose to designate such 1-hop neighbor as a bridge node 308. Insome scenarios, a cluster head node 306 can then use its Tier 2 beaconcommunication service to inform one or more of its selected 1 hopneighbors that they have been designated a network role as a bridgenode. Any remaining nodes of the network which are not cluster headnodes or bridge nodes are considered to be leaf nodes 310. Accordingly,by applying a predetermined set of clustering rules as described herein,a network-spanning communication backbone 312 is established tofacilitate the Tier 1 communications service. Due to the rules regardingthe selection of cluster head nodes 306 and bridge nodes 308, it isensured that all Tier 1 communications propagated though thecommunication backbone 312 can always be heard by all nodes of thenetwork 300, including leaf nodes 310. Communication along the backbone312 can advantageously involve use an avalanche communication method.

The Tier 1 communication service through the communication backbone 312can be used for various purposes. One initial purpose for which theservice can be used is for de-confliction of Tier 1 communications. Tier1 communication conflicts can arise when different cluster head nodeschoose for their transmissions the same set of Tier 1 beacon time slots.Such a communication conflict is undesirable and can make it difficultfor the nodes to communicate. Accordingly, the communication networkdisclosed herein can advantageously provide a de-confliction mechanism.

The precise method applied for de-confliction of Tier 1 beacon time slotusage is not critical and various mechanisms are possible. In all suchimplementations, the goal will be to allow cluster head nodes to quicklyand efficiently gain access to a set of TDMA Tier 1 beacon slots thatare globally conflict-free across the communication backbone. However,in a network solution disclosed herein, the process of de-conflictionwill advantageously occur without the need for centralized controland/or communication with a singular node having overall network controlresponsibility.

For example, in one scenario each cluster head node 306 shown in FIG. 5can share with other cluster head nodes the Tier 1 beacon time slots 206(see FIG. 3 ) that the particular cluster head node has chosen foritself for Tier 1 transmissions. The communication backbone andassociated Tier 1 communication service can be used for suchcommunications. Avalanche communication methods are advantageouslyapplied to facilitate such communications. Cluster head nodes thatreceive such information regarding Tier 1 beacon time slot usage can usesuch data to facilitate de-confliction. For example, a node receivingsuch data can compare a list of Tier 1 beacon time slots that are beingused by other nodes with the receiving node's own selection of Tier 1beacon time slots. If, based on this comparison, a cluster head nodedetects that it is using the same Tier 1 beacon time slots as anothercluster head node, then it recognizes that a conflict exists. In such ascenario, the cluster head node that detects the conflict canautomatically select a different set of Tier 1 beacon time slots for itsown use. To further reduce the potential for such conflicts, eachcluster head node can choose its Tier 1 beacon time slots in accordancewith a randomized selection process. The foregoing de-conflictionprocess can be repeated at regular intervals to ensure that no newconflicts have arisen.

Once a cluster head node has established and de-conflicted its Tier 1beacon time slots it can continue by communicating with other nodes ofthe network. For example, each cluster head can send through thebackbone certain information concerning its one-hop neighbors. Forexample, such information can include the identity or logical name ofeach of such 1-hop neighbors. The self-selection rules which are appliedfor cluster head network role acquisition, ensure that Tier 1communications through the backbone can be received by all nodes of thenetwork. Accordingly, when 1-hop neighbor information is broadcast by acluster head node through the backbone, such information is received byall nodes in the network regardless of whether they are designated ascluster heads, bridges or leaf nodes.

By communicating information about their 1-hop neighbors, each clusterhead ensures that every node of the network will know (1) the identityof all nodes and (2) the route-ability of each node. Further, each nodecomprising the network can determine the number of transmission hopsneeded for a message packet to reach a particular node. The foregoinginformation is then used by all nodes of the network for purposes offacilitating routine communication of network voice and data traffic.

All cluster heads and bridges relay every backbone transmission.Further, Tier 1 communications through the backbone advantageouslyinvolve avalanche communication methods in which two or more nodestransmit the same data concurrently during the same time slot. A nodereceiving both such transmissions will treat the two nearly simultaneousmessages as multipath communications of the same message. This improvesthe chances of reception by the receiving node and has the beneficialeffect of improving bandwidth utilization since both messages arebroadcast at the same time. A further advantage of this avalanche methodof communication is that it allows receiving nodes to imply the identityof the node that originated a particular message. In a network solutiondisclosed herein, certain time slots can be exclusively assigned duringa period of time for use only by certain cluster nodes. Consequently, ifa transmission is detected or received during such time slots, theoriginator of such message may be inferred or implied to be theparticular node which has been assigned exclusive use of such timeslots.

More particularly, a time-slot utilization scheme can be employed inwhich a particular time slot 104 is used by different backbone nodesduring different epochs 106. Every backbone node will ultimately use aparticular numbered time slot but will do so in different epochs. Inthis respect usage of a particular time slot is said to be multiplexed.For example, during a first epoch a particular slot (e.g., time slot 2)may be used by a first node having a first cluster ID. During a secondepoch following the first epoch, the same time slot may be used by asecond node having a second cluster ID. In a third epoch following thesecond epoch, the same time slot may be used by a third node having athird cluster ID. This process can continue until the particular timeslot has been used by all nodes in the network. In the foregoing timeslot utilization scheme, a particular node which uses a time slot willvary with each subsequent epoch. Accordingly, the backbone can employ amultiplexed slot utilization scheme.

With the foregoing arrangement, ownership or use of the same numberedtime slot changes with each iteration of the epoch. Therefore, it isuseful to further designate a particular time slot with a referenceidentification which goes beyond simply referencing the number of thetime slot. For example, the same numbered time slot could berespectively referenced in a first, second and third epoch asmultiplexed slot iteration 1, iteration 2, and iteration 3. However,this language is somewhat cumbersome, and it can sometimes be convenientto refer to the same multiplexed time slot in different epochs by usinga designation referred to herein as either multiplexed slot numbers ormux reference numbers. These mux reference numbers identify anddifferentiate iterations of the same time slot in different epochs.

The foregoing concept is illustrated in FIG. 7 . In this example, a nodewith cluster ID of CID1 can originate data traffic in a particular timeslot (e.g., slot 2) during a first epoch (Epoch 1). This time slot isreferenced in FIG. 7 as multiplexed slot 0 or Mux 0 and is a first datatransmission hop within the network. In the following epoch (Epoch 2),the Tier 1 neighbors of CID1 will forward their traffic in the same timeslot (slot 2). But in Epoch 2 this time slot is referenced asmultiplexed slot 1 or Mux 1. This transmission represents a secondtransmission hop. The third hop will occur in the following epoch (Epoch3). In Epoch 3, the same time slot (slot 2 in this example) is used onceagain for data transmission. But in Epoch 3, this time slot isreferenced as Mux 2.

In the scenario illustrated in FIG. 7 , there are four different clusterhead nodes which respectively have a cluster ID of CID1, CID2, CID3, andCID4. Each cluster head in this example has an assigned set of multiplexslots corresponding to its cluster ID. For example, CID1 is assigned Mux0 in a first epoch (Epoch 1), Mux 1 in a second epoch (Epoch 2), and Mux2 in a third epoch (Epoch 3). After a minimum of three hops, use of thesame three muxs can be repeated. Similar mux assignments are made forCID2 (Muxs 3, 4, 5); CID3 (Muxs 6, 7, 8); and CID4 (Muxs 9, 10, 11).Notably, these muxs use the same time slot (slot 2 in this scenario)that is used by CID1, but they do so in different epochs and thereforehave different mux number references assigned thereto. For example, inEpochs 4, 5 and 6 the same time slot (slot 2 in this example) isrespectively referenced as Mux 3, 4 and 5, and use of these muxes isassigned to CID2. In Epochs 7, 8 and 9, the same time slot (slot 2 inthis example) is respectively referenced as Mux 6, 7 and 8, and use ofthese muxes is assigned to CID3. In Epochs 10, 11 and 12, the same timeslot is respectively referenced as Mux 9, 10 and 11, and use of thesemuxes is assigned to CID4. In this way the same slot is used by clusterhead nodes CID1, CID2, CID3 and CID4. Each such cluster head node hasits own opportunity to transmit a message and to have that messagerelayed.

In FIG. 7 , “Tx” refers to an original transmission of a message M froman originating node. “Relay” refers to a subsequent relay transmissionof the same message by other bridge and cluster head nodes within thenetwork. For example, in the case of CID1 an originating node transmitsa message M in Epoch 1, Mux 0 (E1, MX0). A 1-hop neighbor node of theoriginating node relays the message M at Epoch 2, Mux 1 (E2, MX1), and a2-hop neighbor node of the originating node relays the message M at E3,MX2. A similar process occurs with respect to transmissions originatingfrom CID2, CID3, and CID4. All nodes in the network know which muxes areassigned to a particular cluster head node. Therefore, a node whichreceives a transmission can always infer the cluster head node fromwhich the message originated based on the particular epoch and muxduring which the message is received.

Note that in the above example, there are five relay occurrences foreach TX message and no subsequent transmission of a second message isshown. However, Tier 1 network mux re-use rules allow a source ororiginating node to again transmit after the first data packet hastransited a minimum of three hops. This is permitted because it isassumed that after 3 hops, that any relay transmissions are sufficientlygeographically distant from source node such that the associated relaysignals will be substantially attenuated relative to the source node.Accordingly, a subsequent transmission of another message M2 could occurfrom the originating node CID1 at E4, MX0. To avoid potential confusion,this further message transmission of M2 by CID1 is not shown in FIG. 7 .

Further, in FIG. 7 it may be observed that for each cluster head CID1,CID2, CID3 and CID4 there is a relatively long delay between theoccurrence of Relay 2 and Relay 3. In this regard it may be noted thateach epoch will have some duration (e.g., 30 milliseconds) depending onthe system design. And it is shown that a number of epochs may transpirebetween the occurrence of Relay 2 and Relay 3. Accordingly, it will beunderstood that the first two hops for a transmitted message will occurwith minimal latency, but a longer amount of time is needed before theoccurrence of the 3rd hop. Also it may be noted that the number ofnecessary muxes N is determined by MaxCluster×HopsPerCluster, whereMaxCluster is the maximum number of clusters which may exist in thenetwork and HopsPerCluster is the number of hops permitted before a timeslot can be reused. This number can be set to allow for a minimum of 3hops, but in some scenarios, it may be desirable to allow for a largernumber (e.g., 5 hops) before re-use occurs.

It should further be understood that the mux assignments shown in FIG. 7are merely presented for purposes of illustrating the foregoing conceptand are not intended to be limiting. Other mux assignments methods arealso possible, and all such time slot assignment methodologies areincluded within the scope of a network solution disclosed herein.

Shown in FIG. 8 is an block diagram of a MANET communication node 800which is useful for understanding certain aspects of a communicationsolution described herein. The communication node includes a userinterface 802, an RF transceiver 804, a network interface 805, and aprocessing unit 806. The user interface 802 can include input/outputdevices such as a microphone, a loudspeaker, and a keypad. The userinterface can also include a display unit 812. In some scenarios, anetwork interface device 805 can be provided to allow the node toreceive and transmit data from one or more computing machines comprisinga computer network (not shown). Data and voice communications aretransmitted and received wirelessly at node 800 using RF transceiver804. The transceiver 804 can be configured to communicate throughantenna 814 using a TDMA waveform. Control over such data communicationsare facilitated by the processing unit 806. In some scenarios, theprocessing unit can be configured to cause the node 800 to implement oneor more communications in accordance with the methods and techniquesdescribed herein.

The processor unit 806 can comprise one or more components such as aprocessor, an application specific circuit, a programmable logic device,a digital signal processor, or other circuit programmed to perform thefunctions described herein. Embodiments can be realized in one computersystem or several interconnected computer systems. Any kind of computersystem or other apparatus adapted for carrying out the methods describedherein is suited. The computer system can have a computer program thatcan control the computer system such that it carries out the methodsdescribed herein.

Communication node 800 should be understood to be one possible exampleof a communication node which can be used in connection with the variousembodiments. However, the embodiments are not limited in this regard andany other suitable node architecture can also be used withoutlimitation.

Referring now to FIG. 9 , there is shown a hardware block diagramcomprising an exemplary computer system 900. The machine can include aset of instructions which are used to cause the computer system toperform any one or more of the methodologies discussed herein. In one ormore embodiments, the exemplary computer system 900 can correspond toprocessing unit 806. While only a single machine is illustrated itshould be understood that embodiments can be taken to involve anycollection of machines that individually or jointly execute one or moresets of instructions as described herein.

The computer system 900 is comprised of a processor 902 (e.g. a centralprocessing unit or CPU), a main memory 904, a static memory 906, a driveunit 908 for mass data storage and comprised of machine readable media920, input/output devices 910, a display unit 912 (e.g. a liquid crystaldisplay (LCD) or a solid state display), and a network interface device914. Communications among these various components can be facilitated bymeans of a data bus 918. One or more sets of instructions 924 can bestored completely or partially in one or more of the main memory 904,static memory 906, and drive unit 908. The instructions can also residewithin the processor 902 during execution thereof by the computersystem. The input/output devices 910 can include a keyboard, a mouse, amulti-touch surface (e.g. a touchscreen) and so on. The networkinterface device 914 can be comprised of hardware components andsoftware or firmware to facilitate network data communications inaccordance with a network communication protocol.

The drive unit 908 can comprise a machine readable medium 920 on whichis stored one or more sets of instructions 924 (e.g. software) which areused to facilitate one or more of the methodologies and functionsdescribed herein. The term “machine-readable medium” shall be understoodto include any tangible medium that is capable of storing instructionsor data structures which facilitate any one or more of the methodologiesof the present disclosure. Exemplary machine-readable media can includemagnetic media, solid-state memories, optical-media and so on. Moreparticularly, tangible media as described herein can include; magneticdisks; magneto-optical disks; CD-ROM disks and DVD-ROM disks,semiconductor memory devices, electrically erasable programmableread-only memory (EEPROM)) and flash memory devices. A tangible mediumas described herein is one that is non-transitory insofar as it does notinvolve a propagating signal.

Computer system 900 should be understood to be one possible example of acomputer system which can be used in connection with the variousembodiments. However, the embodiments are not limited in this regard andany other suitable computer system architecture can also be used withoutlimitation. Dedicated hardware implementations including, but notlimited to, application-specific integrated circuits, programmable logicarrays, and other hardware devices can likewise be constructed toimplement the methods described herein. Applications that can includethe apparatus and systems of various embodiments broadly include avariety of electronic and computer systems. Some embodiments mayimplement functions in two or more specific interconnected hardwaremodules or devices with related control and data signals communicatedbetween and through the modules, or as portions of anapplication-specific integrated circuit. Thus, the exemplary system isapplicable to software, firmware, and hardware implementations.

Further, it should be understood that embodiments can take the form of acomputer program product on a tangible computer-usable storage medium(for example, a hard disk or a CD-ROM). The computer-usable storagemedium can have computer-usable program code embodied in the medium. Theterm computer program product, as used herein, refers to a devicecomprised of all the features enabling the implementation of the methodsdescribed herein. Computer program, software application, computersoftware routine, and/or other variants of these terms, in the presentcontext, mean any expression, in any language, code, or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code, or notation; or b) reproduction in a different materialform.

Reference throughout this specification to features, advantages, orsimilar language does not imply that all of the features and advantagesthat may be realized should be or are in any single embodiment. Rather,language referring to the features and advantages is understood to meanthat a specific feature, advantage, or characteristic described inconnection with an embodiment is included in at least one embodiment.Thus, discussions of the features and advantages, and similar language,throughout the specification may, but do not necessarily, refer to thesame embodiment.

Furthermore, the described features, advantages and characteristicsdisclosed herein may be combined in any suitable manner in one or moreembodiments. One skilled in the relevant art will recognize, in light ofthe description herein, that the embodiments can be practiced withoutone or more of the specific features or advantages of a particularembodiment. In other instances, additional features and advantages maybe recognized in certain embodiments that may not be present in allembodiments.

Reference throughout this specification to “one embodiment”, “anembodiment”, or similar language means that a particular feature,structure, or characteristic described in connection with the indicatedembodiment is included in at least one embodiment. Thus, the phrases “inone embodiment”, “in an embodiment”, and similar language throughoutthis specification may, but do not necessarily, all refer to the sameembodiment.

As used in this document, the singular form “a”, “an”, and “the” includeplural references unless the context clearly dictates otherwise. Unlessdefined otherwise, all technical and scientific terms used herein havethe same meanings as commonly understood by one of ordinary skill in theart. As used in this document, the term “comprising” means “including,but not limited to”.

Although the embodiments have been illustrated and described withrespect to one or more implementations, equivalent alterations andmodifications will occur to others skilled in the art upon the readingand understanding of this specification and the annexed drawings. Inaddition, while a particular feature of an embodiment may have beendisclosed with respect to only one of several implementations, suchfeature may be combined with one or more other features of the otherimplementations as may be desired and advantageous for any given orparticular application. Thus, the breadth and scope of the embodimentsdisclosed herein should not be limited by any of the above describedembodiments. Rather, the scope of the invention should be defined inaccordance with the following claims and their equivalents.

We claim:
 1. A method for managing a Mobile ad hoc Network (MANET),comprising: self-assigning by a first node of a plurality of nodescomprising the MANET a role as a part of a network-spanning backboneupon a determination by the first node that one or more criteria havebeen satisfied; using by the first node the network-spanning backbone tofacilitate a first tier control plane communication service within theMANET; communicating by the first node within the MANET using a secondtier control plane communication service separate from the first tiercontrol plane communication service when communicating exclusively withneighbor nodes that are a 1-hop distance from the first node.
 2. Themethod of claim 1, further comprising choosing by the first node one ormore bridge nodes of said first tier control plane communication servicewhich facilitate communication by the first-node with neighbor nodesthat are a 2-hop distance from the first node.
 3. The method of claim 1,wherein the first node uses the network-spanning backbone to facilitatecommunication with all nodes of the network.
 4. The method of claim 1,wherein the role is as a cluster-head in the first tier control planecommunication service, and further comprising choosing by the first nodea cluster ID corresponding to a set of time slots in a Time DivisionMultiple Access (TDMA) waveform.
 5. The method of claim 4, wherein thefirst node uses the network-spanning backbone to facilitatede-confliction of the cluster ID.
 6. The method of claim 4, wherein thefirst node uses the network-spanning backbone to communicate informationconcerning all of its 1-hop neighbors to the plurality of nodescomprising the MANET.
 7. The method of claim 4, wherein the first nodeuses an avalanche communication method to facilitate the first tiercontrol plane communication service in which identification the firstnode as the source of transmitted messages is implied based on the timeslot in which the message is communicated.
 8. The method of claim 1,further comprising claiming by the first node a tier 2 beacon time slotof the TDMA waveform.
 9. The method of claim 8, further comprising usingby the first node the tier 2 beacon time slot to confirm that the tier 2beacon time slot is conflict free within a 2-hop distance of the firstnode.
 10. The method of claim 8, further comprising using by the firstnode the tier 2 beacon time slot to discover its neighbor nodes whichare within a 2-hop distance of the first node.
 11. The method of claim8, further comprising using by the first node the tier 2 beacon timeslot to determine a network role of each of the neighbor nodes within a2-hop distance of the first node.
 12. The method of claim 11, whereinthe first node uses information it has determined concerning the networkrole of each of the neighbor nodes within the 2-hop distance as a basisfor determining whether the one or more criteria have been satisfied.13. A communication node for communicating in a Mobile ad hoc Network(MANET), comprising: a communication transceiver configured tofacilitate wireless communications between the communication node andother nodes of the MANET; a computer processor device configured toself-assign to the communication node a role as a part of anetwork-spanning backbone of the MANET upon a determination by thecommunication node that one or more criteria have been satisfied, thenetwork spanning backbone comprising a plurality of nodes of the MANET;cause the communication node to use the network-spanning backbone tofacilitate a first-tier control plane communication service within theMANET; cause the communication node to communicate within the MANETusing a second-tier control plane communication service separate fromthe first-tier control plane communication service when communicatingexclusively with neighbor nodes that are a 1-hop distance from thecommunication node.
 14. The communication node of claim 13, wherein thecomputer processor device is further configured to choose one or morebridge nodes of said first tier control plane communication service tofacilitate communication by the communication node with one or moreneighbor nodes that are a 2-hop distance from the communication node.15. The communication node of claim 13, wherein the computer processordevice is further configured to cause the communication node to use thenetwork-spanning backbone to facilitate communication with all nodes ofthe network.
 16. The communication node of claim 13, wherein the role isas a cluster-head in the first tier control plane communication service,and wherein the computer processor device is further configured tochoose a cluster ID corresponding to a set of time slots in a TimeDivision Multiple Access (TDMA) waveform.
 17. The communication node ofclaim 16, wherein the computer processor device is further configured tocause the communication node to use the network-spanning backbone tofacilitate de-confliction of the cluster ID.
 18. The communication nodeof claim 16, wherein the computer processor device is further configuredto cause the communication node to use the network-spanning backbone tocommunicate information concerning all of its 1-hop neighbors to theplurality of nodes comprising the MANET.
 19. The communication node ofclaim 16, wherein the computer processor device is configured use anavalanche communication method to facilitate the first tier controlplane communication service in which identification the communicationnode as the source of transmitted messages is implied based on the timeslot in which the message is communicated.
 20. The communication node ofclaim 13, wherein the computer processor device is configured to claimfor the communication node a tier 2 beacon time slot of the TDMAwaveform.
 21. The communication node of claim 20, wherein the computerprocessor device is configured to use the tier 2 beacon time slot toconfirm that the tier 2 beacon time slot is conflict free within a 2-hopdistance of the communication node.
 22. The communication node of claim20, wherein the computer processor device is configured to use the tier2 beacon time slot to discover its neighbor nodes which are within a2-hop distance of the communication node.
 23. The communication node ofclaim 20, wherein the computer processor device is configured to use thetier 2 beacon time slot to determine a network role of each of theneighbor nodes within a 2-hop distance of the communication node. 24.The communication node of claim 23, wherein the computer processordevice is configured to use information it has determined concerning thenetwork role of each of the neighbor nodes within the 2-hop distance asa basis for determining whether the one or more criteria have beensatisfied.